Importance of calibration?

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e-dog

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Since my last newbie question is getting no bites,
I'll post another..

How important is calibration?

I bought a not-great Tascam-22-2 and tried recording
through it, it sounded bad then about six months later
discovered (as i was preparing it for storage) that the
heads were WAY out of alignment.. Visually, like, just
by looking at the heads I could tell they were off.

I bought the unit used and have no idea what they did
to it..

So, I adjusted the heads by sight and then ran a tape
through that I had previously recorded on, and fine-tuned
by sound.. I know that the deck NEEDS to be calibrated,
as the moron adjustments I made helped a lot, BUT I'm
still a bit hesitant to drop $100+ for the appropriate MTR
calibration tape (as i suspect the heads might be of
questionable quality anyway)...

Is the whole nine yards (calibration tape) necessary, or
is there a way to nudge it close to spec by using test
tones out of my soundcard or something??

maybe some kind of pre-calibration, and then if there's
still improvement, the calibration tape? alternatives?

any ideas?




.
 
Well, the obvious answer would be to find another deck that is calibrated and make a tape on that.

Assuming that you cannot go that route, you could try making some test tones on your comp in mono and then convert the file to stereo. That should give you a decent reference point for more of the crude adjustments and allow you to get closer than you are now.

Following that, you could go with a dual trace oscilloscope (I have one that I use for checking power supplies and stuff. The old ones are pretty cheap on ebay). Record some square waves, possibly with a duty cycle that is close to a pulse and you can get scientifically close.

If you do not want to buy stuff for the purpose, you can probably DL some software that will work with your sound card. Just remember that the the mono signal converted to stereo should line up just right and if there is any variance on your tape then you know that you are still off.
 
well if your heads are off so much as to the point of being able to see it, then yes, aligning the heads is essential. It seems though that if your heads are aligned, they don't have to be realigined very often to sound great, and same with calibrating the electronics. When it all comes down to it in my expirience is if if sounds good and you know that it has been calibrated in the past for your kind of tape, it should sound great and you may not be able to hear any difference after hearing it post-calibration.
 
Calib tape rental?

Speaking of calibration, is anybody in the NYC/NJ area interested in lending/renting MRL tapes?
 
e-dog said:
Since my last newbie question is getting no bites,
I'll post another..

How important is calibration?

I bought a not-great Tascam-22-2 and tried recording
through it, it sounded bad then about six months later
discovered (as i was preparing it for storage) that the
heads were WAY out of alignment.. Visually, like, just
by looking at the heads I could tell they were off.

I bought the unit used and have no idea what they did
to it..

So, I adjusted the heads by sight and then ran a tape
through that I had previously recorded on, and fine-tuned
by sound.. I know that the deck NEEDS to be calibrated,
as the moron adjustments I made helped a lot, BUT I'm
still a bit hesitant to drop $100+ for the appropriate MTR
calibration tape (as i suspect the heads might be of
questionable quality anyway)...

Is the whole nine yards (calibration tape) necessary, or
is there a way to nudge it close to spec by using test
tones out of my soundcard or something??

maybe some kind of pre-calibration, and then if there's
still improvement, the calibration tape? alternatives?

any ideas?




.
Click to expand...

You need a standard MRL reproduce calibration tape. If you buy an unknown condition deck off of eBay like the 22-2, 32 or Fostex M20, E-2, etc expect to spend $100.00 - $250.00 easy and lots of time if DIY to get it up to speed.

If you want to dive in you will also need the equipment outlined below.

http://home.swipnet.se/herbalifeinfo/Audio/engmeasure.htm

You will also need the manual for the 22-2.

Someone can make a tape for you from a properly calibrated half-track machine, such as another 22-2, 32, BR-20, Fostex A2, Model 20, E-2. It must be made from a deck set for NAB (IEC2) equalization. Having a tape made is not ideal, but will get you in the ballpark. Making a tape takes an in-depth working knowledge of flux level and equalization standards. It gets complicated because if you want to calibrate the 7-1/2” speed you will need another tape with tones recorded @ -10 dB.

The reason you need a tape of standard tones is for the same reason you need any standard measuring device, such as a ruler, measuring cup, etc. If you record tones on a deck that isn’t true, your calibration will be off by that amount. There is no way around having a calibration tape.

I recommend MRL tape 21J105 for 15 ips to set the machine for 200 nWb/m and use Quantegy/Ampex 407, Maxell XL1 35-90B, or RMGI LPR35.

~Tim
 
So, yes, basically.

If I want the recording to be good, the calibration tape is a must then, huh?

Damn.

I've put way more into this machine than I expected to, and so far, have gotten pretty much nothing back.

Is the "200 nWb/m" the amount of signal that writes to tape?

I read someone on some website somewhere say that they calibrated a similar machine to record hotter, and it "improved" the sound. How do you do that?

Also, I read something about setting bias for bass frequencies, by ear, I think, any idea what that's about?

I guess, while we're at it.. Anyone do opamp upgrades on the record/repro card on a Tascam deck? Resistor or cap upgrades?

Just curious.



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